Cooking is often referred to as an art, not only because of the combination of ingredients that go into a particular recipe, but also due to the skill necessary for proper application and infusion of varying levels of heat over a given period of time throughout the different phases of the food preparation process. Traditional cookware appliances, such as ovens (microwave ovens being an exception), grills, heat lamps and stoves, all utilize the thermodynamic process of conduction to transfer heat from the outer surface of the food item to its interior. This is generally true regardless of the type of heat source used to heat the surface of the food, be it a radiation heat source (i.e. a heat lamp), conduction heat source (i.e. a stovetop), or a convection heat source (i.e. a convection oven or a food dehydrator).
The use of thermometers or other temperature sensors to monitor and control the cooking process is well known. A common thermometer used to monitor and control the cooking process is a probe-type or contact thermometer which is inserted directly into the food item to obtain a temperature of the interior of the food item. Such thermometers are undesirable for use with cookware/servingware objects that have a lid as the use of a probe-type thermometer requires removal of the lid each time a temperature reading is taken. A number of cookware-associated non-contact thermometers have been developed that are attached to, or incorporated into, cookware objects such as pots and pans. For example, my invention disclosed in U.S. patent application Ser. No. 10/833,356, which is incorporated herein by reference in its entirety, provides a means of obtaining consistent and accurate measurement and control of the temperature of a cookware object, such as a pot or pan, by embedding a temperature sensor within a heatable portion of an object, such as within a tunnel through the base of the pot or pan. The temperature sensor is connected to an RFID tag located apart from the heatable portion of the pot or pan. The RFID tag acts as a transmitter (and sometimes as receiver) to communicate with a reader/writer located in a cook-top for heating the object, providing temperature information and other information regarding the object (such as heating characteristics) to the cook-top. The temperature information and the heating information are used by the cook-top to control the temperature of the object.
A pressure cooker is a cookware object such as a pot that includes an airtight lid that seals and locks to the main body of the pot. Food items are placed in the pressure cooker along with liquid (usually water) and the pressure cooker is heated. As the liquid temperature rises, the liquid boils creating steam. The steam is trapped within the pressure cooker by the sealed lid, causing the pressure within the pot to increase. As the pressure increases, the temperature at which the liquid will boil increases resulting in a higher cooking temperature within the pot. This increased cooking temperature reduces cooking time from that obtained by boiling water at atmospheric pressure in unsealed cookware. In addition, steam has a much higher heat transfer potential than a liquid at the same temperature, further decreasing cooking time. A secondary benefit of the increased pressure is that it softens the fibers in foods, tenderizing the food. The increased internal temperature, steam and tenderization of foods cooked under pressure combine to decrease by two-thirds or more of the normal cooking times.
FIG. 1 shows a typical prior art pressure cooker, 10, in which temperature within pressure cooker 10 is regulated by measuring and controlling the pressure within cooker 10. As is shown in FIG. 1, pressure cooker 10 includes typical components found in many pressure cookers, including pressure regulator 20, which is connected to the inner chamber of pressure cooker 10 by vent pipe 30, over-pressure plug 40, sealing ring 50, air vent/cover lock 60, lock pin 70, cover handle 80, and cocking rack 90. Generally, pressure cooker 10 is placed on a stove or other similar heat source and heated until the desired pressure as indicated on pressure regulator 20 is achieved. Once the desired pressure is obtained, the heat is reduced to maintain a constant temperature and pressure within cooker 10. Maintaining a constant temperature and pressure within pressure cooker 10 is often difficult to do manually, taking a considerable amount of trial and error in adjusting the stove temperature. Therefore, it would be beneficial to provide a means of easily regulating/maintaining a constant temperature and pressure within the pressure cooker.
Although my prior invention in which the temperature sensor is embedded within a tunnel in the base, as disclosed in U.S. patent application Ser. No. 10/833,356, and in and U.S. application Ser. No. 11/148,802 filed Jun. 9, 2005 (the disclosure of which is incorporated herein in its entirety), provides a highly effective way of regulating temperature during cooking and may be used in connection with a pressure cooker (as is discussed below), it is most beneficial for use in non-sealed cookware and/or servingware in which the most useful temperature measurement is the temperature at the center of the base of the object where the food items are usually positioned and also where the highest temperature reading will be found. While still important, the temperature at the center of the base of a sealed cookware and/or servingware object, such as a pressure cooker, is secondary to the temperature of the steam created within the pressure cooker. Using the embedded sensor in the base as in my prior invention requires a mathematical extrapolation to determine the actual temperature of the steam within a pressure cooker due to the temperature differential between the interior of the cooker and the temperature of the cooker walls. As the pressure within the pressure cooker is proportional to the temperature, even minor inaccuracies in the temperature measurement can be critical and result in overcooking or undercooking. Therefore, it would be beneficial to provide a means of obtaining a temperature reading from the interior of a pressure cooker for use in regulating/maintaining the temperature and pressure of the cooker.